This invention relates to a method and apparatus for interconnecting electrical circuit elements. More particularly, this invention relates to a new and improved solderless connector and method of using the same for establishing and maintaining electrical contact between multiple layer circuit devices. This invention is particularly well suited for connecting flexible circuits having two or more layers to another flexible circuit, a rigid circuit or an electronic component.
Conventional methods of interconnecting electrical or electronic circuit components consist of the use of separate connector structures and/or soldering terminals on the components to conductors which deliver current to or from the components. While generally suitable for its intended purposes, interconnecting electrical components via separate connector structures does suffer from certain drawbacks and deficiencies including high manufacturing and purchasing costs as well as increased labor time and costs during installation and connection. Similarly, soldering terminals is undesirable as the substrate which supports an exposed terminal must be able to withstand relatively high temperatures with no adverse effects. Also, soldering connections can be time consuming and therefore be labor intensive and expensive. Another problem with soldered connections is the relative difficulty in disconnecting a soldered terminal during repairs and manufacturing.
In some applications it has been found desirable to replace the use of separate connecting structures and/or soldering as a technique for use in establishing connections to flexible and other circuits. In these applications, the requisite electrical contact may be established by mechanically pressing the terminal portions of the circuit against terminal pads on the connector, device or another circuit. Such prior art pressure connections are customarily made with the aid of a solid resilient pressure applicator, such as an elastomeric member, which is placed in compression to bias at least one of the components to be electrically interconnected toward the other component to hold the terminal portions thereof in electrical contact. Such a solderless connection system is disclosed in my earlier U.S. Pat. No. 4,468,074, assigned to the assignee hereof and incorporated herein by reference.
My earlier U.S. Pat. No. 4,468,074 disclosed an apparatus wherein contact portions of a first array of conductive elements are urged against mating contacts of a second array of conductive elements by a pressure applicator comprising a resilient open-celled plastic material thereby establishing and maintaining an electrical connection therebetween. The use of such an open-celled resilient material permits a plurality of closely spaced exposed electrical conductors on or extending from a pair of substrates to be aligned and thereafter reliably pressed together; with the electrical connections being established by a requisite contact pressure applied to the substrates. The solderless connector of U.S. Pat. No. 4,468,074 may be employed to interconnect flexible circuits; to connect flexible circuits to circuits on rigid substrates; to establish connections between the leads extending from integrated circuit in a circuit pattern on a flexible or rigid circuit board; and in other applications.
While suitable for its intended purposes, the solderless connector of U.S. Pat. No. 4,468,074 relates principally to the connection of single layer flexible circuits to other circuit devices. It will be appreciated that flexible circuitry comprising multiple layers of circuits are being increasingly utilized in the electronics industry. Unfortunately, prior art solderless connector devices are not well suited for effecting interconnections involving multi-layer flexible circuits. This is because each successive layer in a multi-layer flexible circuit imparts additional stiffness and rigidity to the flexible circuit as a whole. Consequently, the elastomeric force provided by the resilient pressure applicator becomes less effective leading to unreliable electrical contact.